When it is desirable, as is more and more frequently the case, to keep a machine operating without interruption 24 hours a day, then it is necessary to provide lighting equipment which covers the work area with high-intensity light over an extent which is as wide and as deep as possible.
The current trend in lighting equipment, in particular in work lamps, is thus to multiply the number of lighting sources.
In contrast, ever-increasing rationalization in the design and manufacture of machines means that the number of different types of components used in such lighting equipment should be kept as small as possible.
In order to avoid increasing the number of different spare parts and in order to reduce the number of different suppliers, it is essential, wherever possible, to use these same components from one lamp to another, from one machine to another, and indeed from one range of machines to another.
Further, and above all, it must be possible to repair defective parts on machines that are in service without delay so as to reduce machine downtime to a minimum, since downtime can be extremely expensive.
This aspect becomes more critical for worksites in regions where obtaining spare parts is difficult because of the time required for delivery and the limited stock available on site.
Further, in the special case of lighting equipment, there exist two different types of standard on a world-wide scale, namely European type standards and U.S. type standards.
European standards provide a series of bulbs which, for halogen bulbs, are bulbs of types H1 to H4. These bulb types differ in size and in configuration, and they are removably fittable on bulb-carriers fixed to reflectors, with each bulb-carrier having a special shape adapted to the type of bulb it is to receive.
For example, for H1 or H3 type bulbs, the corresponding bulb-carrier includes facing that extends in a radial plane and receiving the collar on the bulb, whereas for an H2 type bulb, the carrier includes resilient supports extending in an axial plane and receiving fins on the bulb.
Likewise, the way connection is made differs depending on the type of bulb and the associated bulb-carrier: for H1 bulbs, contact blades extend rearwardly from the base, for H2 bulbs, contact is made via the fixing fins, and H3 bulbs have a wire with a connection terminal.
Until recently, the only technique used under U.S. standards was that of "sealed beam" lamps, with each entire lamp constituting a sealed unit incorporated all of the optical components, including the filament which is therefore neither removable nor interchangeable.
This technique which was adopted in 1938 has only very recently (1983) suffered competition from European type systems having interchangeable bulbs: there now exist replaceable bulb lamps for which there are currently three standardized types (9004, 9005, and 9006), and other standards are in the process of being specified, in particular for bulbs running off 24 V (as is the case for most agricultural and worksite machines).
Bulbs satisfying the U.S. standards (one such bulb, type 9006, being shown in FIG. 2) are in the form of a halogen glass bulb mounted on a cylindrical barrel forming the base of the lightbulb, with the barrel being made of insulating material and being provided with a collar which is also insulating (unlike European bulbs since bulbs that have a collar use the collar as the ground contact). The barrel is extended rearwards by a handle (also omitted from European bulbs) enabling the assembly to be grasped and including the electrical feed contacts for the bulb. The base of the bulb also carries an annular sealing ring (not present on European bulbs) which, after a bayonet fitting provided on the collar has been rotated through 1/8th of a turn in the lamp-carrier (which bayonet fitting is also missing from European bulbs), serves to provide complete sealing of the inside volume of the lamp, comparable to that obtained with sealed beam lamps, while nevertheless retaining the option of removing the bulb and avoiding the need for an outer protective cap or other comparable sealing means as is used in European lamps.
From the above, it will readily be understood that the two standardized types of bulb, i.e. European or U.S., are very different from each other, both with respect to their shapes and with respect to the functions they provide (with U.S. bulbs providing an additional sealing function which is not provided by European bulbs, while the mounting collar on European bulbs provides an electrical connection function which is not provided by the collar on U.S. bulbs, etc.).
The main object of the present invention is to provide a mounting system which makes it possible to utilize one or other type of bulb interchangeably, in particular which makes it possible to use a European type bulb or a U.S. type bulb, by providing the following functions simultaneously:
diameter matching; PA1 filament positioning at a given point in the optical system (e.g. the focus of a parabola, or slightly ahead or behind the focus in order to spread the beam in controlled manner); and PA1 retention of the functions specific to each type of bulb (sealing, electrical connection points). PA1 a bulb-carrier fixed to the reflector and defining a radial thrust surface situated at a predetermined distance from the focus of the reflector; PA1 first adaptor means suitable for co-operating with a bulb of the first type, said first adaptor means being provided with an axial bore of a first diameter suitable for receiving the base or support of the bulb, said first adaptor means also including a first contact surface bearing against the reference surface of said first type of bulb, and a second contact surface bearing against the thrust surface of the bulb-carrier, said two contact surfaces being parallel to each other and being at a distance D.sub.1 apart; and PA1 second adaptor means suitable for co-operating with a lamp of the second type, and second adaptor means being provided with an axial bore of a second diameter suitable for receiving the base or the support of a lamp of the second type, said second adaptor means further including a first contact surface bearing against the reference surface of said bulb of the second type, and a second contact surface bearing against the thrust surface of the bulb-carrier, said two contact surfaces being parallel to each other and being a distance D.sub.2 apart, such that, algebraically, D.sub.2 +d.sub.2 =D.sub.1 +d.sub.1. PA1 the bulb-carrier further includes lockable resilient means for forcing the reference surface of the bulb or of its support against the first contact surface of the corresponding adaptor means; PA1 the adaptor means are mounted on the bulb-carrier merely by interfitting, with lockable resilient means serving, in addition, to force the second contact surface against the thrust surface of the bulb-carrier; PA1 the first or second adaptor means further include keying members for determining the angular position of the bulb relative to the axis of the lamp, in particular when the bulb has a transverse filament or when the bulb is provided with incorporated masking means defining a cut-off; PA1 the first or second adaptor means are electrically conductive and further include electrical connection members for establishing an electrical connection with the metal reference surface of the bulb, which surface constitutes one of the feed terminals thereof; PA1 a sealing ring is also provided interposed between the bulb-carrier and the first or second adaptor means; and PA1 the axial bore of the first or second adaptor means has an inside surface suitable for co-operating with sealing means provided on the facing portion of the bulb or of the bulb-carrier.
An object of the invention is to provide such a system which is universally applicable, cheap to manufacture, and simple in structure.
So long as a system is simple, it can be used by maintenance or repair personnel without requiring special training, in particular by virtue of the fact that even when the type of bulb in a given lamp is changed, the optical characteristics of the lamp are not changed and there is therefore no need to readjust its beam.
Since the system is cheap, it is possible firstly to fit a universal system on initial manufacture instead of fitting a system which can receive only one type of bulb, without significantly increasing the cost of the lamp.
It is then possible, secondly to accompany each spare bulb, e.g. in the same package as the bulb, with its specific adaptor part enabling it to be mounted on a lamp fitted with a universal mounting system of the invention. The cost of the spare part is not significantly increased since the major portion of the manufacturing cost of a bulb plus adaptor set is constituted by the cost of the bulb per se, and the maintenance operative need not trouble to find out beforehand whether a defective lamp was previously fitted with a bulb of the same type as the available spare or with a bulb of another type, since in any event the package containing the spare also contains event the required adaptor.
Stock control problems are thus reduced both for manufacture and for maintenance, and the two sources (initial manufacture and subsequent replacement) may be totally distinct and may provide bulbs of different types. Thus, a European manufacturer of lighting equipment can produce complete lamps fitted with readialy available European bulbs and then ship these equipments to manufacturers who can in turn sell machines fitted in this way throughout the world regardless of whether the bulbs readily available in any given country happen to be U.S. type bulbs or European type bulbs.
In the context of this example, if a faulty lamp is to be repaired in a country where the readily available bulbs are U.S. type bulbs (or if the person carrying out the repair only has U.S. type bulbs in stock), then it is necessary merely to remove the originally-installed European bulb together with its specific adaptor and replace them with the U.S. type bulb and its specific adaptor. Once the bulb-and-adaptor assembly has been locked into place, it is certain that the optical characteristics of the lamp will be identical with what they were before (since the mounting system of the invention makes it possible to retain the relative positions of the various optical parts in spite of the different shapes of the bulbs); in addition, in this particular example of replacement by means of a U.S. type bulb, the inside volume of the lamp will be reliably sealed, as is typical for lamps fitted with U.S. type bulbs.